1. Field of the Invention
This invention relates generally to semiconductor products manufacturing, and, more particularly, to a method and apparatus for monitoring and performing improved focus methods for photolithography processing of semiconductor devices.
2. Description of the Related Art
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Today""s manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and therefore, require a number of inputs that are generally fine-tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (etching, doping, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and specialized that the processes may be performed in different manufacturing locations that contain different control schemes.
Among the important aspects in semiconductor device manufacturing are RTA control, chemical-mechanical (CMT) control, etching, and overlay control. Overlay is one of several important steps in the photolithography area of semiconductor manufacturing. The overlay process involves measuring the misalignment between two successive patterned layers on the surface of a semiconductor device. Generally, minimization of misalignment errors is important to ensure that the multiple layers of the semiconductor devices are connected and functional. As technology facilitates smaller critical dimensions for semiconductor devices, the need for reduction of misalignment errors increases dramatically. Errors in photolithography processes are also caused by inadequate focusing during exposure steps.
Generally, photolithography engineers currently analyze the overlay and misalignment errors a few times a month. The results from the analysis of the overlay and misalignment errors are used to make updates to exposure tool settings manually. Generally, a manufacturing model is employed to control the manufacturing processes. Some of the problems associated with the current methods include the fact that the exposure tool settings are only updated a few times a month. Furthermore, currently the exposure tool updates are performed manually. Many times, errors in semiconductor manufacturing are not organized and reported to quality control personnel. Often, the manufacturing models themselves incur bias errors that could compromise manufacturing quality.
Generally, a set of processing steps is performed on a lot of wafers on a semiconductor manufacturing tool called an exposure tool or a stepper. The manufacturing tool communicates with a manufacturing framework or a network of processing modules. The manufacturing tool is generally connected to an equipment interface. The equipment inter-face is connected to a machine interface to which the stepper is connected, thereby facilitating communications between the stepper and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script based upon a manufacturing model, which can be a software program that automatically retrieves the data needed to execute a manufacturing process. Often, semiconductor devices are staged through multiple manufacturing tools for multiple processes, generating data relating to the quality of the processed semiconductor devices. Many times, errors can occur during the processing of semiconductor devices. These errors can cause appreciable inconsistencies in the critical dimensions of multiple parameters in the processed semiconductor devices. Many times photolithography processes are performed outside an acceptable focus window, causing degradation in the quality of manufactured semiconductor devices. Manual monitoring of manufacturing parameters during photolithography processes can improve focus during exposure process but can result in some focus errors.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a method is provided for performing automatic control adjustments during photolithography processes. A plurality of semiconductor devices are processed. Optical data analysis is performed upon at least one of the processed semiconductor devices. Control adjustments to the processing are performed in response to the optical data analysis.
In another aspect of the present invention, an apparatus is provided for performing automatic control adjustments. The apparatus of the present invention comprises: a processing tool capable of processing semiconductor devices; an optical sensor coupled with said processing tool, said optical sensor being capable of acquiring optical manufacturing data during the operation of said processing tool; a machine interface electronically coupled with said processing tool and said optical sensor such that said machine interface is capable of delivering a control signal to said processing tool and receiving the optical manufacturing data from said optical sensor; a metrology tool coupled with said processing tool, said metrology tool being capable of receiving a processed semiconductor wafer from said processing tool and performing metrology data acquisition upon said processed semiconductor wafer; and a system electronically interfaced with said machine interface and said metrology tool, said system being capable of receiving data from said machine interface and sending a control signal to said machine interface.